Receiving a test result that is not a clear “positive” or “negative” can be confusing. For Herpes Simplex Virus Type 2 (HSV-2) serology, this unclear finding is often labeled as “equivocal.” This result means the standard blood test could not make a definitive call on your infection status, leaving you in a medical gray zone. It neither confirms nor rules out HSV-2. Understanding the specifics of this result and the necessary next steps is essential. This article will demystify the equivocal HSV-2 test result and provide information for follow-up testing.
Defining the Equivocal Result
An equivocal result indicates that the amount of HSV-2 antibodies detected falls within a predetermined indeterminate range. The standard screening test is a type-specific Immunoglobulin G (IgG) antibody assay, which measures the body’s long-term immune response. These tests report a quantitative Index Value. A result below the lower threshold (often around 0.90) is negative, while a result above the upper threshold (typically 1.10 or higher) is positive. The equivocal “gray zone” falls between these cutoffs, frequently ranging from 0.90 to 1.09. This mid-range reading suggests antibodies are present, but at a level too low for a definitive positive diagnosis. The test cannot reliably distinguish between a true low-level positive and a non-specific reaction, meaning the initial screening was inconclusive.
Causes of Ambiguous Test Readings
Timing and Seroconversion
The primary reason for an equivocal HSV-2 result relates to the timing of the test relative to a potential infection. If exposure occurred recently, the immune system may have just begun producing IgG antibodies. These levels may be too low for a clear positive but high enough to push the Index Value into the equivocal gray zone. This period is known as seroconversion, which can take a few weeks up to several months for antibodies to reach fully detectable levels.
Cross-Reactivity and Immune Variation
Cross-reactivity is another common cause, particularly in individuals who already have Herpes Simplex Virus Type 1 (HSV-1). Since HSV-1 and HSV-2 are structurally similar, the screening test can sometimes mistakenly detect high levels of HSV-1 antibodies, resulting in an equivocal reading for HSV-2. Individual variations in immune response can also lead to ambiguous readings, even years after infection. Some people naturally produce lower levels of HSV-2 antibodies, causing their concentration to perpetually hover near the test’s cutoff threshold.
Recommended Follow-Up and Confirmatory Testing
An equivocal HSV-2 result necessitates a specific retesting strategy to achieve a definitive diagnosis. The first step is repeating the type-specific IgG test after four to twelve weeks to allow for potential seroconversion. If the infection was recently acquired, this waiting period allows antibody concentration to increase, pushing the Index Value into the positive range. If the repeat test remains equivocal or is a low-positive (Index Value between 1.1 and 3.5), confirmatory testing is recommended.
The gold standard for confirming indeterminate serology is the Western Blot assay. This highly specific test separates and identifies viral proteins, providing a more accurate picture than the standard screening assay. The HSV-2 IgG inhibition assay is an alternative method used to distinguish a true low-positive result from a false-positive caused by cross-reactivity. Until a final diagnosis is established, it is important to discuss the equivocal result with a healthcare professional regarding implications for sexual health.